X4
Pharmaceuticals, a clinical stage biotechnology company developing
novel CXCR4
inhibitor drugs to improve immune cell trafficking to treat cancer
and rare disease, today announced the first clinical data from the
open-label Phase 2 portion of an on-going Phase 2/3 study of X4P-001-RD,
an investigational treatment for patients with WHIM syndrome, a primary
immunodeficiency disease.

The objectives of the Phase 2 portion of the study is to evaluate the
safety and efficacy of X4P-001-RD and to assess the dose required to
achieve a consistent increase in circulating neutrophils and lymphocytes
in patients with WHIM syndrome. The preliminary results from the study
demonstrated promising activity with dose-dependent increases in
neutrophil and lymphocyte counts in patients with WHIM syndrome. All
patients enrolled in the study to date had meaningful increases in the
levels of circulating white blood cells with daily oral administration
of X4P-001-RD. X4P-001-RD was considered to be safe and well tolerated.
Dose escalation continues to evaluate potential further increases in
white blood cell counts. The data were presented at the 59th Annual
Meeting of the American Society for Hematology (ASH) on December 9, 2017
in Orlando, Florida.

“Based upon the etiology of WHIM Syndrome, CXCR4 antagonism by
X4P-001-RD should improve the primary pathophysiology underlying the
disease,” said Dr. David C. Dale, MD, Professor of Medicine and former
Dean of the School of Medicine at the University of Washington Medical
Center and lead investigator of the study. “We are encouraged by the
meaningful increases in white blood cell counts and look forward to
observing how it correlates with other disease parameters in this
severely immuno-deficient patient population.”

Results from the first 5 patients with genetically confirmed WHIM
Syndrome who were enrolled in the dose escalation portion of the ongoing
Phase 2/3 study (as of data cutoff date of October 16, 2017) were
presented. Highlights of the poster presentation include:

All patients demonstrated a dose-dependent increase in neutrophils and
lymphocytes from screening values, with lymphocytes increasing in
greater proportion than neutrophils

X4P-001 drug exposure showed a dose-dependent increase correlated to
the increases in neutrophils

X4P-001 was well-tolerated, with no severe adverse events (AEs)
observed

Dose escalation is continuing in the Phase 2 portion of the study

“X4P-001-RD shows promising increases in white blood cell counts, a
primary biomarker for response to therapy, in each of the WHIM patients
we’ve studied to date,” said Sudha
Parasuraman, MD, Chief Medical Officer of X4. “We look forward to
sharing further data supporting our recommended Phase 3 dose and plans
for further development in 2018 as we continue to advance this novel
oral treatment for patients with WHIM.”

WHIM syndrome is a primary immunodeficiency disease (“PID”) caused by
genetic mutations in the CXCR4 receptor gene resulting in susceptibility
to certain types of infections. WHIM is an abbreviation for the
characteristic clinical symptoms of the syndrome: Warts,
Hypogammaglobulinemia, Infections, and Myelokathexis. Within the overall
category of primary immunodeficiencies, there are between 15,000 and
100,000 patients in the US that are classified with PID of unknown
origin — of which WHIM is one.1,2,3 WHIM syndrome is a rare
disorder and the precise prevalence or incidence of patients that have
the genetic mutation responsible for WHIM syndrome is unknown. Because
patients are highly susceptible to infections, WHIM syndrome is
associated with significant morbidity beginning in early childhood and
continuing throughout life. Current therapy is limited to treatment of
acute infections with antibiotics or prevention through the use of
intravenous immunoglobulin or G-CSF. There is no approved therapy for
the treatment of WHIM syndrome.

About X4P-001-RD for Primary Immunodeficiency Disease

X4P-001-RD,
an oral, small molecule inhibitor of CXCR4, or C-X-C receptor type 4, is
being developed for use as a life-long treatment for patients with WHIM
syndrome and other primary genetic immunodeficiencies. X4P-001-RD is
currently being studied in a Phase 2/3 trial in patients with WHIM
syndrome. Within the bone marrow, a normally functioning CXCR4 receptor
controls the release of neutrophils and leukocytes into the blood
stream, thereby ensuring normal immune surveillance functions throughout
the body. In patients with WHIM syndrome, mutations to the CXCR4
receptor cause aberrant signaling leading to retention of neutrophils
and leukocytes in the bone marrow and inadequate immune surveillance and
function.4,5 X4P-001-RD is designed to normalize the
signaling for the mutant CXCR4 receptor to promote the release of
neutrophils and leukocytes, thereby restoring healthy immunity.

About X4 Pharmaceuticals

X4
Pharmaceuticals is developing novel therapeutics designed to improve
immune cell trafficking to treat cancer and rare diseases. The Company’s
oral small molecule drug candidates inhibit the CXCR4 receptor, a
pathway which plays a central role in immune surveillance. X4’s most
advanced product candidate, X4P-001-RD, is in a Phase 2/3 study in
patients with WHIM syndrome, a rare genetic, primary immunodeficiency
disease. X4P-001-IO is currently under investigation in multiple Phase
1/2 studies in refractory clear cell renal cell carcinoma (ccRCC) and
melanoma. X4 was founded and is led by a team with deep product
development and commercialization expertise, including several former
members of the Genzyme leadership team, and is located in Cambridge, MA.

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